Gnats infesting my house

Q. I have little gnats infesting my house. What are they? How can I get rid of them?

Dave from East Palestine

A. After asking Dave a few more questions, we were able to determine more details about the insects and how they got into his house. It seems Dave took his houseplants outside for the summer, then brought them back inside for the winter. This is a common occurrence for those of us who like plants and take them in and out of the house. They can come from new houseplants purchased from the store or nursery as well.

The gnats are fungus gnats. Adult females probably laid eggs in the soil of the house plants before they were brought into the house. The eggs can hatch in just under a week, with the larvae feeding in the soil for about two weeks. They pupate and emerge as adults in a week. The adults can fly around for more than a week before the life cycle is complete. Just a few eggs produced a few adults after five weeks in the house. Now that we are three months past the first frost – the infestation may have grown to be quite bothersome.

Thankfully, they are clumsy fliers, so a flyswatter becomes a tool of choice. But, there’s probably no way to keep them all under control. They fly past your face just when you thought they were all gone. They life cycle can keep going if nothing is done. They are harmless to humans and pets.

The best way to manage them is inspecting plants before they are purchased or brought back inside at the end of summer. Clean up dead leaves and debris in the containers. Keep an eye on the containers to watch for these little black gnats hovering around.

If you have an infestation, water management is the best way to rid them from your home. House plants should never be on a watering schedule. They don’t get ‘one cup of water every Monday.’ They should only be watered once the soil turns dry. Use your finger to check the moisture level. When infestations are high, allow the plants to dry out completely. Wait until the plant begins to show signs of drought stress before watering again. The lack of water inhibits the growth of fungi in the soil, the source of food for the larvae.

Complete details and additional controls are available at http://go.osu.edu/fungusgnat.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Winter hours for the Plant and Pest Diagnostic Clinic vary. Submit questions to the clinic at 330-533-5538 or drop samples off to the OSU Extension Office in Canfield.